U.S. Pat. No. 4,969,310 issued Nov. 13, 1990 to Hershey Lerner et al. under the title Packaging Machine and Method and assigned to the assignee of this patent (the SP Patent) discloses and claims a packaging machine which has enjoyed commercial success. One of the major advantages of the machine of the SP Patent resides in a novel conveyor belt mechanism for gripping upstanding lips of bags of a chain as they are transported along a path of travel and registered at a load station. The firmness with which the lips are gripped makes the machine highly suitable for packaging bulky products which are stuffed into the bags. While the machine of the SP Patent was an advance over the prior art, especially in terms of its lip gripping capability, even greater lip gripping capabilities, if achieved, would be useful in enabling packaging of additional products. Expressed another way, the bag gripping forces of the machine of the SP Patent were dependent on clamping pressure applied between pairs of belts. Thus, while the machine was a definite advance over the art, as to any given bag size, it has a finite maximum stuffing pressure it can withstand without slippage.
Since the bag gripping is dependent on the force with which belt pairs are clamped, the length of the path of travel through the load station is limited. Thus the length of a bag along the path of travel is limited, loading of a bag while it moves along the path of travel is not possible and the concurrent loading of two or more bags is not available.
With the machine of the SP Patent there is an intermittent section which includes the loading station and a continuous section which includes a sealing station. Since the section including the loading station is intermittent, obviously the through-put of the machine is inherently less than could be achieved with a continuously operating loading section.
The machine of the SP Patent had further advantages over the prior art, including an adjustable bag opening mechanism which was adapted to accept a wide range of bag sizes and adjustable to provide a range of bag openings. While an advance over the prior art, the bag openings were six sided so that, like most of the prior art, a rectangular bag opening was not achievable.
Although one prior machine provides rectangular openings, the dimensions of the rectangular openings, both longitudinally and transversely, are limited both by the construction of the chain of bags being filled and by guide rods used to transport the bags. Thus, if an operator wished to change from one opening size to another, another and different web of bags was required. Moreover, to the extent, that the packaging machine could be adjusted to vary the configuration of the rectangular opening, such available adjustment was extremely limited because it required substitution of a different set of guide rods. Further, there was excessive packaging material waste in the form of elongate tubes which slid along the guide rails.
While the machine of the SP Patent has been sold under the designation SP-100V for vertical orientation in which products can be gravity loaded into bags and the designation SP-100H for horizontal loading of stuffable products, neither machine was suitable for adjustment from horizontal to vertical and return, nor for orientation at selected angles of product insertion between the horizontal and the vertical.
A problem has been experienced with prior art sealers having pairs of opposed belts to transport bags through a seal station. The problem is that too frequently due to weight of the products there is slippage of bags relative to the belts and sometimes of the bag fronts relative to the backs resulting in poor seal quality. Alternatively or additionally it is too often necessary to provide a conveyor or other support for bags as they are transported through the sealer station.